ST. PETERSBURG, Fla. — John McCain took command of the Republican presidential race Monday night with a solid win in Florida—a big-state victory that answers some of the most important doubts that have shadowed his candidacy.

Before Florida, McCain could not boast of winning any major contest limited to Republican voters. Now he can boast away, since he won here without relying on the independents and crossover Democrats who powered him so far this year and in his failed campaign eight years ago.

Exit polls indicated it was still moderates and those who identified themselves as "somewhat conservative" who provided the bulk of McCain’s support over former Massachusetts Gov. Mitt Romney, who trailed by five percentage points.

And with Rudy Giuliani’s reported decision to exit the race and throw his support to McCain, the Arizonan is now in even better position to reap these voting blocs in next week’s massive Super Tuesday primaries. McCain's success in Florida came in part because of the collapse of Giuliani, who waged everything on the Sunshine State. Fading in the polls, the former mayor declined to attack McCain, allowing the Arizonan to pick up some of the votes Giuliani lost as his prospects diminished.

There are still more questions ahead for McCain, chief among them whether a Republican so many conservatives have so many reservations about might yet stumble in next week’s Super Tuesday primaries, and whether even if he takes the nomination he can unify a party that has become weakened and demoralized in the Bush years.

But there is no longer any doubt that he is the clear front-runner in GOP race — indeed the only contender not resting his hopes on exotic, carom-shot scenarios.

Now it is Romney — McCain’s chief tormentor in Florida and elsewhere — who will have to check his gut, and his wallet, to decide how vigorously he intends to compete on Super Tuesday after a five-point loss here.

Unlike Giuliani, Romney is plainly staying in the race for now, aides said. But one Romney adviser said the candidate has made no decision yet on whether to reach deeper into his personal fortune to buy Super Tuesday advertising.

"The decision whether to [keep self-funding] will have to be made in the next 24 hours," this source said.

While Romney has demonstrated a willingness to spend his own cash — he's estimated to have dropped at least $40 million so far — he has also shown a hesitation to throw good money after bad, pulling the plug on costly ads in Florida and South Carolina after he lost New Hampshire to McCain.

Romney is pinning his hopes on somehow fashioning an open-field race with McCain for the support of the GOP’s traditional conservative base.

But it seems unlikely for the moment that he will get such a head-to-head contest for conservatives — and not entirely obvious that he would win it even if he does.

Former Arkansas Gov. Mike Huckabee, a Baptist preacher and favorite of many social conservatives, has indicated he is staying in the race, despite a fourth-place finish here. He took just over 13 percent of the vote in Florida, and can expect to run credibly in Feb. 5 Southern states like Alabama, Georgia, Oklahoma, Tennessee and his native Arkansas — all with high concentrations of evangelical voters.

Florida exit polls found a majority of Huckabee voters saying they would have voted for McCain if their candidate had not been in the race. This challenges the Romney camp’s assertion that Huckabee is getting in the way of Romney getting a clean shot at McCain.

What’s more, the Florida exit polls suggested a grudging — and still tentative — coming to peace with McCain by the most conservative Republicans. In 2000, McCain lost people who consider themselves “very conservative” by 7-to-1 against George W. Bush. This year, he lost them by a 2-to-1 ratio.

McCain tried to encourage this stages-of-grief process in his Miami victory speech, linking his maverick views to the president this generation of conservatives admires most.

He said he was drawn to politics by a leader with “a reputation for standing by his convictions no matter the changing winds of political thought and popular culture.

“When I left the Navy and entered public life, I enlisted as a foot soldier in the political revolution he began. And I am as proud to be a Reagan conservative today, as I was then,” McCain exulted.

Unlike earlier in the race, the 71-year-old McCain was unqualified in raising expectations for his own performance next Tuesday.

“My friends, in one week we will have as close to a national primary as we have ever had in this country,” he said. “I intend to win it and be the nominee of our party.”

The first stop on this strategy is California, where he will hold fundraisers and participate Wednesday in a debate, co-sponsored by Politico, CNN, and the Los Angeles Times, at the Ronald Reagan Presidential Library.

Then he’ll begin a five-day fly-around of many of the states holding contests on Tuesday, weaving fundraisers in between retail stops.

Particularly in light of the Giuliani exit, McCain could sweep the four winner-take-all Northeastern states — New York, New Jersey, Connecticut and Delaware. These could combine with his native Arizona, and a sizable chunk of delegates in California to leave Romney on Feb. 6 with no plausible path forward for the nomination.

Speaking to reporters after his candidate’s concession speech, Romney spokesman Kevin Madden pointed to the only bright spot after their loss: exit polls showing McCain’s continued weakness with conservative voters.

To exploit this, Romney adviser Ben Ginsberg said that their Super Tuesday strategy would be to pick up delegates in states most hospitable to conservative voters. That means states that are holding caucuses or conventions likely to draw party activists such as Minnesota, Colorado, Montana and North Dakota.

It also means focusing on those contests that are limited to only Republicans, such as California, Missouri and Oklahoma.

California — the big enchilada prize, with 173 delegates — is forbidding terrain for both top contenders. The delegates are apportioned by congressional district.

In a closed primary where conservative Republicans may come out against McCain because of his immigration views, this could be a significant obstacle to the Arizonan. But with the ability to succeed in more liberal or moderate districts, McCain will at worst split the Golden State’s delegates.

Lastly, whatever decision Romney makes about tapping his personal wealth to tap to buy ads, with so many states voting and McCain enjoying a “free media” bounce in news coverage, the impact could be limited.

McCain’s goal is to prevent the contest from becoming a climactic battle for the philosophical soul of the party. Romney’s is to encourage this, on his terms.

“Are we a [liberal] Rockefeller Republican Party or are we the party of Ronald Reagan?” was how Rep. Tom Feeney (R-Fla.), a Romney backer, pitted the choice.

“Our movement has to make a choice,” added Jay Sekulow, another Romney backer and Christian conservative leader.

But Feeney acknowledged that if McCain clearly defeats Romney on Feb. 5, the GOP will rally behind him.

The Florida exit polls further illuminated the choice. Among the highlights:

*McCain ran strongly with both suburban and rural voters, and among the least and most educated. He won people with post-graduate degrees by 10 points, while narrowly losing the six in 10 voters with only undergraduate education.

*Age played a role. Voters 65 and older made up a third of the electorate, and they backed McCain by 7 percentage points.

*Forty-five percent said the economy was the most important issue facing the country. That was nearly twice as many as Iraq or illegal immigration.